Research Neoteny. Some peoples have succeeded at self domestication more than others.
https://www.quora.com/Human-Evolutionary-Genetics-Why-do-some-white-people-have-flat-butts-Or-why-does-it-seem-some-people-of-African-ancestry-have-larger-butts-What-is-the-physical-difference-in-the-bodies-that-determines-the-body-shape
